1. Field of Invention
This invention relates to transmitting rotational power efficiently by matching input speed and torque with output requirements. A positive engagement continuously variable transmission (PECVT) has no restriction on the number of gear ratios as in conventional transmissions. Instead it has a continuous range of gear ratios. This invention will mostly be used by the motor vehicle industry.
2. Discussion of the Prior Art
Despite the technological advancement in the motor vehicle industry, the standard transmissions used in motor vehicles are not efficient, that is the available power of the engine can only be delivered to the wheels at certain vehicle's speeds. Major engine and vehicle manufacturers are constantly seeking improved technique for transmitting power efficiently from a vehicle's engine to its wheels. Two main types of continuously or infinitely variable transmissions(CVT or IVT) are being investigated by the industry. These types are the belt and the traction drives. The belt type CVT (basically two variable diameter pulleys connected by a belt) whether push, pull, fabric-reinforced rubber or multi-segmented steel drive belt has low torque-carrying capabilities which limits its application to vehicles with low power requirements. It also needs a starting device such as a torque converter or a multi-plate clutch to smooth the loads encountered when starting the vehicle from rest. Furthermore, very strong and exotic materials are required in manufacturing belt type CVT due to the high loads imposed on its internal mechanism, sliding wear surface and contact fatigue.
On the other hand is the traction drives(IVT) which basically consists of two rotating conical steel rollers that transfer torque between themselves through viscous shear of a thin film of lubricant, or uses a pivotal traction roller inter-spaced between an input and output torroidel discs. The major problem associated with the traction drives is durability which result from high surface fatigue that occur on the traction element. Other problems are associated with the excessive weight, high cost and limiting factors such as fluid issues.